I am installing the new 81.5mm piston, rings, etc. on the fl400r. The top center of the wiseco piston is stamped with the size and an arrow pointing to the outside piston edge. Does the arrow point to the intake or exhaust side?

The ring gap side goes to the intake side. The arrow should point to the exhaust but have seen wiesco make a mistake and stamp it wrong. So make sure the ring gap side faces the intake

Exactly shoubadaba hit the nail on the head and is 100% right!

Purge your brain of markings on top of pistons and reload your brains with the fact ALL the ring gaps will be on the intake side of the cylinder.

I have not seen one yet where they face the gaps on the exhaust side has anybody else?

don't forget to prep the piston viewtopic.php?f=1&t=3399

And the port bevel viewtopic.php?f=1&t=3702&p=27154

Thanks to both Shoubadaba and Hoser!
The additional info on piston prep helped also. I had read the other posts about rounding the sharp edges, not these.
Again, thank-you.

I believe Polaris does it.

Looking at the angle of the port opening it looks like the intake side of a piston port Engine to me.